1. Field of the Invention
This invention relates to high energy gas lasers and, more particularly, to a subsonic flow aerodynamic window in a high energy gas laser system.
2. Description of the Prior Art
In the art, low energy lasers contain windows with physical walls made of materials that transmit the laser wavelength, such as a Brewster window. But, in a high energy gas laser, such a material window would be disintegrated by the laser beam. Therefore, a window must be designed which would permit passage of a laser beam with no physical obstructions and which would prevent a flow of ambient gas into the laser optical cavity. Such an aerodynamic window is described in U.S. Pat. No. 3,617,928, issued to George Hausmann, entitled "Aerodynamic Window for Gas Dynamic Laser," filed May 23, 1968. Another U.S. Pat. No. 3,654,569, entitled "Aerodynamic Window," filed Dec. 23, 1968, also describes an aerodynamic window with no physical walls. These prior windows were invented for use in lasers having cavity pressures typically less than 1/10 of the ambient pressure, in which case the window must have a supersonic jet. The present invention is intended for lasers in which the cavity pressure is on the order of 9/10 of the ambient pressure, in which case the aerodynamic-window jet need not be supersonic.